Offshore wind energy is a very promising source of renewable energy for the reason that offshore wind is more intense and uniform than on-land wind. To harness wind energy in deeper water further offshore, one solution is to build floating wind turbines. Floating wind turbines face technical challenges that are different from both on-land wind turbines and floating oil and gas platforms.
Different from onshore wind turbines, a floating wind turbine requires a platform that provides buoyancy to support the weight of the whole structure. The structure of the platform may have several cylinder-shaped columns with large diameters. Besides providing buoyancy, the platform combined with the wind turbine generator should be able to resist dynamic wind, wave and current load, and provide a stable support for power production. Another challenge is the added fatigue damage from wave load, which might be comparable to that due to wind load. This requires a robust structural design to achieve better reliability.
One unique challenge of designing floating wind turbines, when compared to floating oil and gas platforms, is that a large load is transferred from the tower of the wind turbine generator to the platform through a very concentrated location at the tower base connection. The columns of the platform usually have much larger diameters than the tower of the wind turbine generator in order to provide buoyancy. The traditional way to strengthen the tower base connection with the floater's deck is to reinforce with large amount of welded stiffeners, which may not be cost efficient. Compared to the oil and gas industry, offshore wind energy production has a much smaller profit margin. One goal of structural design is to minimize the weight and cost of the structure. Therefore, simplified stiffening on the platform columns is preferable.
Thus, there is a need for offshore wind turbines to have a structural platform design that provides load bearing capacity, hydrodynamic stability and good reliability with minimized cost.